Where the Numbers Come From

The General Bathymetric Chart of the Oceans is the canonical global ocean-depth dataset, jointly maintained by the IHO and IOC of UNESCO. The "sub-ice" variant uses BedMachine and Bedmap2 ice-shelf draft estimates so the Ross and Filchner-Ronne shelves resolve to bedrock rather than ice surface — material when planning Southern-Ocean acoustics. MuirWave uses GEBCO for the depth lookup at every pin and as the bottom boundary for the ray solver.

Licence

Placed in the public domain by the GEBCO project — free to copy, adapt, and use commercially, subject to acknowledgement, non-endorsement, and no-misrepresentation of the data. Not to be used for navigation or where loss of life could result. (verified 2026-07-13)

Role in app

Depth lookup at every scenario pin; bottom-bounce geometry for the ray solver.

Bundled

17.8 MB at 5 arc-min global (baseline IPA); HQ regional packs add 200 MB – 1 GB per basin.

NOAA NCEI's quarter-degree climatology of temperature, salinity, dissolved oxygen, nitrate, phosphate, and silicate — averaged over decades of in-situ casts and re-gridded at 1° (Compact) and 0.25° (HQ). MuirWave uses the temperature and salinity columns as the input to Mackenzie's nine-term sound-speed equation and as the basis for Francois-Garrison absorption.

Licence

Public domain — US Government scientific data, no copyright restrictions.

Role in app

Temperature + salinity columns for sound-speed and absorption calculations.

Bundled

89 MB at 1° global, 24-level (baseline IPA); HQ packs add 0.25° at 72 levels per region.

Mackenzie's nine-term polynomial relating temperature, salinity, and depth to sound speed is the workhorse formula for ocean-acoustic codes. Accurate to about 0.07 m/s over the full oceanographic envelope — finer than WOA23's underlying observations warrant, so the bottleneck is data, not formula. MuirWave applies it column-by-column at every pin.

Citation

Mackenzie, K. V. (1981). "Nine-term equation for sound speed in the oceans." JASA, 70(3), 807–812.

Role in app

WOA23 T/S/depth → c(z) sound-speed profile; input to the ray solver.

Status

Equation reimplemented in Swift; underlying maths not copyrightable, paper cited as canonical reference.

The Dutkiewicz dataset is a digital map of seafloor lithology — calcareous ooze, siliceous ooze, pelagic clay, etc. — derived from ~14,500 surface samples and gridded for global coverage. MuirWave uses it to look up sediment class under every pin, which then keys into the Hamilton-1980 fluid-half-space reflection model.

Citation

Dutkiewicz, A., Müller, R. D., O'Callaghan, S., Jónasson, H. (2015). "Census of seafloor sediments in the world's ocean." Geology, 43(9), 795–798. Gridded dataset: PANGAEA, doi:10.1594/PANGAEA.932412.

Licence

Creative Commons CC BY-SA 4.0 (Attribution-ShareAlike). Commercial use permitted with attribution; adaptations must be shared under the same licence.

Our derived layer

MuirWave's bundled sediment raster is an adaptation of this dataset — resampled to a 0.1° grid and reclassified into MuirWave's sediment categories. Per ShareAlike, we offer that derived raster under the same CC BY-SA 4.0. (verified 2026-07-13)

Role in app

Sediment-class lookup at every pin; drives bottom-loss model.

Bundled

25 MB global classification grid.

Hamilton's geoacoustic regressions relate a sediment's mean grain size to its density, sound-speed, and attenuation — the parameters that set how much acoustic energy is lost at each bottom bounce. MuirWave combines these published regressions with the classical Rayleigh fluid–fluid reflection coefficient (Brekhovskikh; Jensen, Kuperman, Porter & Schmidt) to compute bottom loss versus grazing angle and frequency. The physics is drawn entirely from the open scientific literature and re-implemented independently in Swift.

Citation

Hamilton, E. L. (1980). "Geoacoustic modeling of the sea floor." JASA, 68(5), 1313–1340.

Status

Published scientific equations and regressions — not copyrightable as such — re-implemented independently in Swift; article text and figures not redistributed.

Role in app

Sediment grain size → geoacoustic parameters → Rayleigh bottom-loss vs. grazing-angle and frequency.

The two-paper Francois-Garrison set is the canonical model for sound absorption in seawater as a function of temperature, salinity, depth, pH, and frequency. It captures the boric-acid relaxation around 1 kHz and the magnesium-sulphate relaxation around 100 kHz, both critical for sub-100-kHz marine-acoustic work. MuirWave applies it at every range bin in the transmission-loss integral.

Citation

Francois, R. E. & Garrison, G. R. (1982). "Sound absorption based on ocean measurements" — Parts I & II. JASA, 72(3), 896–907 & 72(6), 1879–1890.

Role in app

α(f, T, S, p, pH) absorption coefficient — applied per range bin.

Status

Equations reimplemented in Swift; papers cited.

Wenz's 1962 paper laid out the spectral structure of ocean ambient noise — the wind-driven component above ~500 Hz, the shipping component in the 50-500 Hz band, biological and seismic at lower frequencies — and his curves remain the operational reference 60+ years later. MuirWave composes the wind term from live wind speed and the shipping term from a modelled shipping-density climatology to produce a frequency-dependent NL at the receiver.

Citation

Wenz, G. M. (1962). "Acoustic ambient noise in the ocean: spectra and sources." JASA, 34(12), 1936–1956.

Role in app

Frequency-dependent ambient noise level (NL) for the sonar equation.

Status

Spectra reimplemented from the published curves; paper cited.

The standard graduate-level textbook on ocean-acoustic numerical methods. MuirWave's ray solver is built from the eikonal-tracing scheme described in Chapter 3, with surface-bottom-CZ classification and dynamic-ray-equation amplitude tracking per the same chapter. No code from the textbook's accompanying Bellhop/Kraken/RAMGeo distribution is used — only the equations.

Citation

Jensen, F. B., Kuperman, W. A., Porter, M. B., Schmidt, H. (2011). Computational Ocean Acoustics, 2nd ed. Springer. ISBN 978-1-4419-8677-1.

Role in app

Eikonal ray-trace algorithm, dynamic-ray amplitude tracking, surface/bottom/CZ ray classification.

Status

Equations reimplemented in Swift; bundled Bellhop/Kraken/RAMGeo NOT linked.

NMFS's 2024 Update (Version 3.0) sets the marine-mammal hearing-group auditory-weighting functions and the received-level thresholds for the onset of temporary and permanent threshold shift (TTS / auditory injury). It is the operative US regulatory criterion behind incidental-take analysis and most marine-EIA underwater-noise assessment. MuirWave applies the v3.0 weighting functions and onset thresholds to turn a transmission-loss field into hearing-group-weighted impact ranges.

Citation

NMFS (2024). 2024 Update to: Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 3.0). NOAA Technical Memorandum NMFS-OPR.

Role in app

Hearing-group weighting + TTS / injury onset thresholds for impact ranges.

Status

Public-domain US-Government guidance; criteria reimplemented in Swift, document cited.

The Southall et al. 2019 review underpins the hearing-group structure (low-, high- and very-high-frequency cetaceans, sirenians, and pinnipeds in water and in air) and the auditory-weighting and exposure recommendations that the NMFS guidance builds on. MuirWave uses its hearing-group definitions when weighting the field for non-US assessments and cross-checks.

Citation

Southall, B. L., et al. (2019). "Marine Mammal Noise Exposure Criteria: Updated Scientific Recommendations for Residual Hearing Effects." Aquatic Mammals, 45(2), 125–232.

Role in app

Hearing-group definitions and weighting basis.

Status

Published criteria reimplemented in Swift; paper cited.

The ASA-accredited Popper et al. 2014 guidelines provide the fish and sea-turtle exposure criteria — by hearing category and injury / mortality endpoint — that complement the marine-mammal criteria in a full EIA. MuirWave applies them to produce fish and sea-turtle impact ranges alongside the marine-mammal ranges.

Citation

Popper, A. N., et al. (2014). Sound Exposure Guidelines for Fishes and Sea Turtles. ASA S3/SC1.4 TR-2014. Springer.

Role in app

Fish + sea-turtle exposure criteria for impact ranges.

Status

Published criteria reimplemented in Swift; guidelines cited.

The Hybrid Coordinate Ocean Model run by the US Naval Research Laboratory provides daily nowcast and forecast fields of temperature, salinity, and currents at 1/12° resolution. MuirWave's data service fetches fresh temperature and salinity columns to refine the WOA23 climatology when a connection is available, and the app falls back to the bundled climatology when offline.

Licence

Public domain — US Government scientific data.

Role in app

Fresh T/S column overlay on top of WOA23 climatology; optional, never required.

Status

Served through MuirWave's own data service; source fields from tds.hycom.org.

Surface wind and waves from NOAA's GFS and GFS-Wave models are the input to the wind-driven term of the Wenz noise spectrum. When online, MuirWave reads the 10-metre wind speed at the pin location, derives a sea-state, and feeds it into the noise calculation; offline, the user selects sea-state manually. The fields are served through MuirWave's own weather proxy (weather.muirwave.com), not fetched from any third-party weather API.

Licence

Public domain — US Government scientific data.

Role in app

Wind speed → sea-state → wind-driven Wenz noise term.

Status

Served through MuirWave's own weather service; optional, never required.

A modelled global shipping-density climatology underpins the shipping component of the Wenz ambient-noise spectrum. Higher-density basins (e.g. the Strait of Malacca, North Sea) get a 5-15 dB correction in the 50-500 Hz band over near-empty water.

Citation

Halpern, B. S., et al. (2015). Cumulative human impacts to the world's ocean — commercial-shipping intensity layer. NCEAS / Knowledge Network for Biocomplexity (KNB). Exact dataset record + DOI to be pinned from the acquisition log.

Licence

Creative Commons CC BY 4.0 — attribution required, commercial use permitted. (licence verified 2026-07-13; dataset record pending)

Status

Approximated from static shipping-density climatology.

Role in app

Shipping-band Wenz noise term.